When a Pokémon with Protosynthesis is in harsh sunlight or is holding Booster Energy, its highest stat (other than HP and taking into account stat stages, but not held items) is increased by 30%, or 50% if Speed is the highest stat. Upon activation, a message tells which stat is increased to all the players. If multiple stats are tied for highest, Protosynthesis breaks the tie by prioritizing Attack, Defense, Special Attack, Special Defense, and Speed, in that order.
Protosynthesis will activate in harsh sunlight even if the Pokémon is holding a Utility Umbrella, but not if a Pokémon with Air Lock or Cloud Nine is on the field. Harsh sunlight will activate Protosynthesis before a held Booster Energy, so the Booster Energy will not be consumed if the Pokémon with Protosynthesis is in harsh sunlight. If activated by weather, the effect of Protosynthesis will end when the field is no longer affected by harsh sunlight. Protosynthesis's stat increase cannot be passed by Baton Pass.
Skill Swap and Doodle will fail if either Pokémon has Protosynthesis. Gastro Acid and Role Play will fail if the target has Protosynthesis; however, Simple Beam and Worry Seed will work. Protosynthesis cannot be copied by Receiver, Trace and Power of Alchemy or replaced by Lingering Aroma. If a Pokémon obtains Protosynthesis with Imposter or Transform, the Ability will not activate regardless of if the Pokémon is in harsh sunlight or holding a Booster Energy.
